1. Field of the Invention
The invention generally relates to line control devices and, more specifically to a failsafe system raising and lowering at least one object.
2. Description of the Prior Art
One traditional or common device for securing a line from advancing relative to a reference point is a cam cleat that includes a support structure through which the line passes and one or two pivotally mounted cams within the structure that can move between a first position in which the cam(s) permits the line to move along a given direction and a second position in which the cam(s) engages the line by applying pressure to it to prevent the line from advancing in an opposite direction with respect to a support structure.
Known cams generally have had a thickness that substantially corresponded to the diameter of the line and have been provided with a series of spaced teeth or ridges that are generally transverse to the direction of movement of the line. When the movement of the line needed to be halted the cam was rotated to contact the line and the teeth penetrated and deformed the line within a confined passageway to create a pressure and/or friction that prevented the line from advancing. However, traditional cleats of this type have a number of disadvantages. For example, such cleats normally require numerous operative parts, including a spring that normally urges the cam to be biased into contact with the line. As such, the line must normally be manually inserted into the cleat by moving the cam to a non-locking position against the action of the spring. The need for numerous working parts makes the cleat more costly to manufacture and more susceptible to failure. Assembly of the cleat and its numerous parts contributes to the high cost of manufacture.
Because the cams typically have a thickness that approximates the diameter of the line being controlled such cleats tend to be large and bulky. Also, the cams need to be molded or cast to provide the desired cam thicknesses and, thus, cannot be made of relatively thin sheet material. Also, a serious problem is the damage that traditional cleats cause to the lines that are controlled. Because the lines are locked in place when the relatively sharp teeth edges or ridges of the cams penetrate and deform the lines by applying substantial transverse forces that bite across the fibers or strands of the line, the sharp teeth frequently damage the strands or fibers forming the lines by and, with time, the teeth of the cams deteriorate the integrity of the strands or fibers and, therefore, also of the lines as well. Repeated or continued uses of the cleat frequently render the lines unsuitable for extended use. This not only jeopardizes the operation and safety of the apparatus on which the cleat is used, such as a machine or sailboat, for example, but also requires regular replacements of the lines. This is a further inconvenience and costly operation.
In U.S. Patent Application No. 61/201,817, assigned to the assignee of the subject application, a cam formed of planar material and devices using the same are disclosed. However, the pulley or sheave is not always optimum for desired applications, including systems for raising and lowering potted plants, bicycles and other objects as they are not constructed from an optimal number of reduced parts or components. Such construction(s) increase the costs of manufacture and hence the cost to the consumer. Also, some of the components described in the aforementioned application are sometimes difficult or inconvenient to mount onto a ceiling or a wall.